The present invention relates generally to the field of multi-duty helmets and, particularly, to helmets designed for both the protection of the wearer and for the mounting of auxiliary equipment.
Various types of headgear are presently available for the use of tank, aircraft, mining personnel, etc., such as hard shell helmets designed for the mounting of auxiliary equipment. The large size of these helmets renders them particularly unsuitable for use as communications helmets since the attachment of communications equipment such as transceivers, ear defenders and microphones, in effect, merely add bulk and weight to the already cumbersome helmets. These auxiliary equipments produce excessive pressure on nerves and blood vessels in various areas of the skull and, therefore, are not tolerable by the wearer for any length of time. In general, they are physiologically unsound. This combination of excessive weight and bulk also results in a curtailment of range of movement of the head and neck of the wearer. When the helmets are designed for use in a noisy environment they are usually lined with heavy padding to provide noise attenuation. Actually, the pads limit voice communication without adequately protecting or insulating against high-level noise. A further disadvantage lies in the high cost of these helmets. This is primarily caused by the individual fit required because of the unique size and contour of the particular individual skull. Heretofore the size adjustments have been limited to changing the diameter of a horizontal band, commonly termed a sweat band, going completely around the helmet just inside the helmet opening. The limitation encountered with this design is that while the horizontal diameter of the skull is taken into consideration, no consideration is given to accommodating the individual contour or shape of the skull. Thus, the prior art helmets must be individually fitted which results in a greatly increased cost on a large quantity basis. Another factor adding to the overall cost is the necessity for replacement helmets when an auxiliary equipment attached thereto requires maintenance or adjustment, i.e. the auxiliary equipment is not readily detachable.
An existing communications helmet, the AN/PRC-56 utilized by the U.S. Navy, includes radio electronics contained in the ear pods. This approach suffers from several disadvantages. For instance, the radio enclosure volume is necessarily limited which severely limits the sophistication of radio circuitry. As a result, electronic design compromises are necessitated which make the radio susceptible to damage. Additionally, the radio enclosure is fully exposed to impacts which are encountered in normal use which obviously makes the radio more susceptible to mechanical damage. That design also suffers from the disadvantage that the majority of the radio weight is borne by the headband thus creating a severe pressure point at the top of the user's head, causing discomfort. The fact that the radio is part of the ear pods and is not attached to the helmet suspension system also causes excessive weight moments felt by the user. Moreover, that design has no standby provisions for the hearing defenders or goggles. These items bear heavily on the user's head in use to form an effective seal which is important to the protective features of the helmet. However, there is no way of relieving pressure or eliminating perspiration buildup during stand-down periods short of doffing the entire helmet.
A critical shortcoming of most prior art helmet designs is that they provide no direct means of mounting the goggles. Usually, the goggles are worn with an elastic strap which must pass over the hearing defenders. This, of course, increases the pressure on the head from the hearing defenders.
There are also a wide variety of commercial protective helmets, especially for industrial use, for contact sports and for vehicle sports. Despite this variety, these helmets all require helmet shell sizing (usually as small, medium and large). Furthermore, the shells of these helmets are based on spherical head-shape approximations, they do not combine all the protective features required for a combined high noise, high wind, bump-severe, and flying object environments, they do not lend themselves to integral communications packaging (except in designs that restrict head or body motions) nor can the electronics be easily removed for servicing, and standby provisions for goggles and ear defender assemblies are either limited or non-existent.
Hearing defenders are absolutely required for persons working in high noise environments as around jet aircraft, especially if they must use a communications system as on a flight deck. The hearing defender effectiveness in attenuating noise depends on the design of the hearing defenders, the characteristics of the ear seal, the pressure holding the defenders in place and the ability of the hearing defender to conform to head shape. While hearing defenders are essential in high noise, they are an annoyance in quiet. The hearing defender pressure must be relieved periodically when the use period is beyond an hour or so. Also, hearing defenders cover over the user's head around the ears where there are abundant blood vessels. This means that perspiration is likely to collect inside the hearing defenders, causing irritation. Consequently, a hearing defender standby position is desirable to relieve pressure and perspiration during breaks and standby periods. Hearing defender pressure must be at least two pounds to keep the hearing defenders sealed in the peak ambient noise levels. Noise above 130 dB(c) is capable of vibrating the hearing defender sufficiently to break the seal unless the minimum force is maintained. On the other hand, pressures above 4 pounds are very uncomfortable and cannot be tolerated for very long. The hearing defender mounting system must hold the hearing defenders sufficiently rigid to keep the hearing defenders from sagging off the head under their own weight and under even pressure to force the ear seal to work properly. At the same time, however, the mounting system must be flexible to accommodate head size variations. Some prior art hearing defender mounts include fixed mounts which attach the hearing defenders directly to the helmet with degrees of freedom which allow the hearing defender to conform to head shapes. Other mounting systems provide a linkage between the helmet and the hearing defenders. This linkage usually consists of a spring lever arm and a swivel of some sort on the helmet or a tab mechanism which attaches to the helmet, the hearing defenders and a chin strap. The problems posed by a spring lever arm/swivel design include maintaining mounting pressures within the usable range (2-4 lbs.) across the full range of head variations, establishing a design which does not suffer from fatigue from the stresses in the lever arm, and keeping forces on the helmet below the long-term damage level. The tab mechanism cannot adjust to as wide a range of head sizes as a lever arm, requires the use of a chin strap, and can create locally excessive stresses on the helmet.
Current protective goggles are mounted with an elastic headband. This headband must be worn either inside the helmet, which complicates donning, or outside the helmet, which may interfere with goggle fit and will upset proper hearing defender pressures. In either case there is not normally a full satisfactory standby position for headband mounted goggles. Headband mounted goggles interfere with the normal functioning of other helmet elements because the headband must pass directly above the ears where hearing defenders must seal and suspension system components must rest. Other methods of goggle mount have been attempted, including spring hinges of various sorts and swivel arrangements. These other methods suffer from one or more of the following deficiencies: lack of adjustment range; lack of pressure to hold the goggles in place in high winds and during normal working movements; they require specially designed goggles and they may interfere with the use of eyeglasses. In addition, some of these methods cannot be made rugged enough and are impractical to manufacture in quantity.